The interface between a device and its operator is an important, though sometimes underemphasized, feature of the device. As a device includes more operating functions, it becomes increasingly important to consider how such a device may be operated and controlled by an operator. Improvements are of little value if an operator is unable to utilize and implement the improvements. Such inability can result from a lack of understanding of how the improved capabilities are used or from frustration at previous attempts to utilize these features.
The present invention relates to devices which are used to determine the location and orientation of concealed underground conductive objects. Determining the location of such concealed objects as underground gas, sewer and water pipes, power cables, and telephone and CATV cables or conduits is a necessary prerequisite to excavation and/or the laying of new lines, pipes or cables. For simplicity, these underground objects are hereinafter referred to as underground "lines." In some applications, an underground steerable boring tool is utilized to form an underground tunnel through which underground lines are subsequently routed. While utilizing the steerable boring tool, it is important for an operator to trace or keep track of the relative location of the existing underground lines with respect to the boring tool, in order to avoid contacting the existing lines with the tool. In other applications, a trench is excavated and lines are subsequently placed in the open trench. While excavating these trenches, it is equally important for an operator to know the locations of any existing lines in order to avoid contacting them with the excavating equipment.
Special-purpose electromagnetic field detector systems, which are commonly called "locators," have been used for many years to locate and/or trace the path of concealed underground lines. Various types of locators exist, but receivers that detect electromagnetic signals radiating from either the underground lines or a small transmitter located within the boring tool are by far the most widely used. Such radiated signals are generally produced in two ways: (1) an alternating current signal from an above-ground transmitting source is induced into a conductive line thereby generating an electromagnetic field around the line; or (2) a signal is radiated from a small transmitter either mounted inside a boring tool or positioned within a non-conductive line.
Because locating, distinguishing and tracing multiple, concealed underground lines has become increasingly time consuming and costly, it would be desirable to provide more flexible locating techniques and equipment. An improved locating system is described in commonly assigned, copending application Ser. No. 539,851, entitled "An Improved System For Locating Concealed Underground Objects", which application is incorporated herein by reference. As discussed above, it would be desirable to provide an operator interface which permits an operator to take full advantage of the capabilities of this improved system.
Another aspect of the operator interface relates to how information is presented to the operator. Underground boring and line tracing is almost wholly dependent on information presented to an operator. On the basis of this information, the operator determines where digging and boring will be done. Since prior art transmitters and receivers for locating systems have generally included a single analog meter, only a limited amount of information can be presented to an operator. As transmitter locators and receivers become more complex, it would be desirable to provide the operator with more information. Further, it would be desirable to provide this information in a format which is easily recognized and understood by the operator.
The single analog meter of the prior art also presents a problem in determining both the points of maximum and minimum signal. Operators of prior art locators typically observe a needle on the meter while walking with the locator in their hand while attempting to find the place where the signal strength is greatest by a trial and error technique. Some locators have a mode where the source is located by a null or minimum in signal strength. It is very difficult to detect small differences in signal strength since merely moving the locator can cause needle movement. Some prior art locators have a loudspeaker or earphone through which the operator can hear the signal being received. The loudness of the signal is an aid in determining where the signal is strongest. However, the ear is not sensitive to small differences in amplitude and thus the above problems with respect to the analog meter also occur here.
The operator interface also relates to the reliability, convenience, and overall ease of use of the device. Existing locator transmitters and receivers have a number of deficiencies in these areas. Some receivers incorporate a non-metallic pipe structure to house the antennas, and these receivers are inherently prone to job-site damage. Other receivers have a broad "wand" containing circuitry and antennas which provides structural strength but catches the wind and makes it difficult for the operator to hold the receiver in a proper vertical position on windy days.
In addition, some existing receivers have a first mode to trace utility lines and a second mode to track the position of "moles" or underground transmitters. These receivers must be held at an awkward angle by the operator in at least one of the modes of operation. This problem results from the fact that the detected magnetic field has a different orientation depending on whether it is produced by a buried conductor or an underground transmitter. The antennas in the receiver must be held by the operator in a particular orientation relative to the magnetic field. If the receiver is constructed to be convenient for use in detecting magnetic fields from one type of source, such construction will be inconvenient for use in detecting fields from the other type of source.
Also, controls on existing prior art transmitters and receivers are often difficult to use, requiring the operator to use both hands to control and operate the instrument. Typically, the operator must turn knobs to adjust various instrument settings. In a receiver, for example, this is accomplished carrying the receiver in one hand and adjusting the settings in the other. This is both distracting and awkward for the operator.